1. Field of the Invention
This invention relates to hydraulic pumps and to hydraulic pump assemblies useful in lubricating systems for railway tracks.
2. The Prior Art
Hydraulic pumps are well known devices useful in many different applications. One application where such pumps are useful is in lubricating systems for railway tracks wherein the pump operates to deliver grease from a storage tank to a nearby railway track when an actuator element located adjacent the track is operated by the wheel of a railway vehicle passing thereover. A lubricating system of this type is disclosed in U.S. Pat. No. 4,334,596.
The operational reliability of such hydraulic pumps is of great importance, and investigations into alternative and improved mechanical constructions are an ongoing endeavor.
The present invention is directed to hydraulic pumps which can be used in lubricating systems for railway tracks and which are reliable, simple in construction, and easy to repair, and to lubricating systems using such pumps.
The inventive hydraulic pump, hereinafter described as a rotociprocating pump, includes a housing which defines an inlet chamber for hydraulic fluid, an inlet port leading to the inlet chamber, an outlet channel extending from the inlet chamber to an outlet port for hydraulic fluid, a gear chamber containing interengaged gears for delivering lubricant such as grease from a storage tank through the gear chamber to a discharge chamber having a discharge port, and a double headed piston which extends from the inlet chamber to the discharge chamber, a first head of the piston being located in the inlet chamber and a second head being located in the discharge chamber. A shaft which extends between the heads extends through a bore in a wall of the housing which separates the inlet chamber from the discharge chamber. A spring is located around the shaft to bias the piston in a first position wherein the first head is spaced a maximum distance from the wall and the second head is located against a opposite side of the wall. In a second position of the piston the first head thereof is located nearer the wall (compressing the spring) and the second head of the piston is located away from the wall and closer to the discharge port.
The outlet port has a smaller cross sectional dimension than that of the inlet channel such that an equivalent volume of hydraulic fluid pulsed through the inlet port into the inlet chamber cannot immediately pass through the outlet channel and out of the outlet port. A one-way check valve is located between the inlet chamber and the outlet channel to prevent back flow of hydraulic fluid from the outlet channel into the inlet chamber. A relief valve is associated with the outlet channel to provide for blow-off of hydraulic fluid in the event of overpressure.
In operation, after the rotociprocating pump has been primed, such that grease has filled the gear chamber and is contained in the discharge chamber, and hydraulic fluid is in the inlet chamber and the outlet channel, a checked pulsed flow of hydraulic fluid into the inlet chamber through the inlet port will result in a flow of hydraulic fluid from the inlet chamber into the outlet channel and in movement of the double headed piston from its first position to its second position, forcing grease out of the discharge chamber and through the discharge port. After the pulsed flow of hydraulic fluid has ceased, the spring will cause the piston to move back to its first position, concurrently causing more hydraulic fluid to flow from the inlet chamber through the outlet channel and out of the outlet port.
A pump assembly for use in a lubricating system includes the rotociprocating pump and a hydraulic motor connected to the gears of the pump, as well as a conduit which connects the outlet port of the pump to a hydraulic motor so that hydraulic fluid flow through the conduit will cause rotation of the gears in the pump. Thus, movement of the double headed piston from its second position to its first position will cause the hydraulic motor to operate and the interengaged gears to rotate and reload the discharge chamber with grease. The grease discharged from the discharge port will be conveyed through a conduit to nearby railway track(s). See U.S. Pat. No. 4,334,596.
The rotociprocating pump of the invention, as well as the pump assembly that includes the rotociprocating pump, is extremely reliable and durable, and requires infrequent servicing.